Mac Pro 2013 Constant Thermal Shutdowns

Just did a full teardown and reapplied thermal paste to the cpu. Looks like whoever did it last didn't put enough on. I dusted the rest of the spots that were more on the inaccessible side and now I'm getting 10-30 degrees difference. However the problem still happens. It gets further in the export test, but it fails at 10 degrees lower than last time at 150F.

The previous shutdown cause is now giving me a 0 error (power loss) consistently for the past five tries. No new panics in the diagnostic log. I am plugged into a UPS on battery so I changed to straight into the wall and it still happens. I'm wondering if it's a dying power supply potentially getting not enough juice on prolonged power strains like this.

I feel like the app you sent is much more accurate. I tested several things to stress the computer out. I played several games just to see if it would crash and they were semi-intensive. (Should be enough to make it shut down) and nothing happened after three straight hours of gameplay. Highest temps were CPU PECI @ 145F, CPU Sensor 3 @145F, GPU 2 @ 130, and GPU 1 @114.

After that I went to editing again. On a 10 minute export of 4k h.264 footage in Final Cut I recorded the temps right before it crashed. Ambient 2 @ 87F, CPU PECI @ 160F, CPU Sensor 4 @ 156F, GPU 1/2 @ 132F, Dimm 1-4 @ 114F, PSU Secondary/Controller @ 122F, SSD @ 100F. This was the same video I was exporting getting 120F from SMC Fan Control so my original reading was pretty off.

Since I switched to Macs fan control I now have a constant "Previous Shutdown cause 5" in terminal.

As another note if it helps, I get the multi-language "Your computer shut off from an error" black screen.

These temps are all at max speed for fans. The computer is sitting on top of a monitor riser that lifts it off the table and a notebook cooler that's fan is the same size as the fan on the mac. It's probably the best possible cooling without going ridiculous. On a desperate attempt to see if it would work, I used a box fan about two feet from it in conjunction with this setup to push cool air but it only slows down the heat up process and still crashes.

It showed that there were two code 5 shutdowns the other day with all of the 3 error code shutdowns as well, but it was a 2/10 time thing. I did a clean install of mojave and am up to date (I just updated from the update this week about 30 minutes ago but it still looks like its going to crash.

I haven't actually looked at these yet. I just did another export test to see if this last update helped and it didn't change anything. However, it looks like all of the crash reports minus one of them are all from quicklook and quicklook satellite.

Process: SafariQuickLookPreview [991]

Path: /Applications/Safari.app/Contents/PlugIns/SafariQuickLookPreview.appex/Contents/MacOS/SafariQuickLookPreview

Identifier: SafariQuickLookPreview

Version: 1.0 (1)

Code Type: X86-64 (Native)

Parent Process: ??? [1]

Responsible: SafariQuickLookPreview [991]

Termination Reason: DYLD, [0x4] Symbol missing

I have a feeling you're right. I plan on testing any and all software first just to make sure, but Sunday I plan on reapplying thermal paste to the processor if I can't find a solution by then. If that doesn't work I might hold out until Apple stores open again.